1. Field of the Invention
The present invention relates to a hydraulic shovel concurrently used for crane operations.
2. Description of the Prior Art
A hydraulic shovel concurrently used for crane operations is comprised of a lower running body and an upper turning body that is mounted onto this lower running body via a turning mechanism such that it may freely turn, wherein an implement is provided on the upper turning body. The implement includes a boom, an arm and a bucket. And the hydraulic shovels concurrently used for crane operations of this type are provided with a hook at a tip end portion of the implement for enabling crane operations. More particularly, the bucket is pivotally attached to the arm via a swinging mechanism such that, for instance, the hook is suspended from a pivot shaft comprising a part of this rocking mechanism.
A safe-working load for loads to be suspended is preliminarily set for suspending operations performed during crane operations, and it is necessary to take care that an actual load with a member to be suspended being in a suspended condition will not exceed this safe-working load. For this purpose, a load display monitor was conventionally provided for displaying the actual load or the safe-working load on this load display monitor so as to inform an operator of these loads. It is further necessary to confirm engine conditions of this hydraulic shovel concurrently used for crane operations for which purpose another monitor screen was required. More particularly, in performing ordinary excavation operations, it was sufficient to keep track of engine conditions such as cooling water temperature for the engine, engine oil temperature or the amount of fuel remaining and others to ascertain the condition of the entire vehicle whereas the load conditions need to be ascertained in addition to the above when performing crane operations to be sure to keep track of the condition of the entire vehicle body. In other words, when performing crane operations, load conditions acting on the vehicle body besides engine conditions function as factors that largely affect the entire vehicle body, and it will be a premise for performing stable operations to keep track of this load conditions as well.
However, since the load display monitor was provided at a different position than the monitor screen for watching the engine conditions so that the operator may not observe these two in a simultaneous manner that led to difficulties in operations and complications in confirming conditions when performing crane operations.
Moreover, since only the actual load or safe-working load was displayed on the above-mentioned load display monitor, the operator needed to judge by himself or herself on the basis of these numeric values whether the vehicle is in a dangerous condition or not which may have led to delays in operating speed. It has thus conventionally been developed for an overload preventing and alarming device, which was provided either in addition to the above-mentioned load display monitor or singly, for generating alarm sounds in case the suspending load (actual load) reached, for example, 90% of the safe-working load for the particularly posture. However, even though the arrangement may be that such alarm sounds are generated, it may happen that the operator may not hear them owing to noise or other factors at site so that it was impossible to inform the operator of dangerous conditions in a stable manner. In performing suspending operations during crane operations, problems are presented in that contact between hooks and buckets causes damages in the hooks and buckets or inconveniences in suspending members to be suspended by the hooks (hook contact problems) and the like in addition to the problem of overload. It was, however, conventionally the case that alarm means was employed that was capable of only informing that a dangerous area has been reached in view of the problem of this hook contact and the like.